Barbed prosthetic knit and hernia repair mesh made therefrom as well as process for making said prosthetic knit

ABSTRACT

The present invention relates to a prosthetic knit based on at least a first yarn of biocompatible polymer material defining first and second opposite and openwork faces, and on at least a second biocompatible and heat-fusible monofilament yarn, forming barbs that protrude outwards from at least said first face and are obtained by melting loops generated by said second yarn, the chart followed for the knitting of said first and second yarns on a warp knitting machine having three guide bars B 1,  B 2,  B 3  being the following, according to the ISO 11676 standard:—Bar B 1:  1.0/0.1//—Bar B 2:  1.0/7.7/6.6/7.7//—Bar B 3:  2.1/5.5/3.4/0.0// said second yarn following the chart of bar B 3.  The present invention also relates to a process for manufacturing such a knit.

The present invention relates to a prosthetic knit equipped with barbs,capable of being rolled up on itself, then unrolled effortlessly. Such aknit can particularly be used for producing wall-reinforcing prosthesesintended to be introduced into a patient by coelioscopy.

Wall-reinforcing prostheses, for example prostheses for reinforcing theabdominal wall, are widely used in the surgical field. These prosthesesare intended to treat hernias by temporarily or permanently filling atissue defect. These prostheses are generally made of biocompatibleprosthetic fabric and can have a number of shapes, for examplerectangular, circular or oval, depending on the anatomical structure towhich they are to be fitted. Some of these prostheses are made fromentirely bioresorbable yarns and are intended to disappear after havingcarried out their reinforcing role while cell colonization takes placeand tissue rehabilitation takes over. Other prostheses comprisenon-bioresorbable yarns and are intended to remain permanently in thebody of the patient.

Some of these prostheses are made from an arrangement of yarns, a knit,a woven fabric or non-woven fabric, comprising barbs that protrudeoutwards from one face of the prosthesis: these barbs constitute hooksthat are able to fix themselves either in another prosthetic fabric,belonging to the same prosthesis or not, or directly in the biologicaltissues, for example the abdominal wall.

Furthermore, for the sake of minimizing the traumatisms subsequent toany surgical operation, patients are increasingly often operated on viacoelioscopic surgery when the type of operation carried out permits it.Coelioscopic surgery requires only very small incisions, through which atrocar is passed, within which the prosthesis is conveyed to theimplantation site. Thus open surgery is avoided and the patient canleave hospital rapidly. Coelioscopic surgery is particularly popular insurgical operations carried out in the abdomen, such as for example thetreatment of hernias.

However, the trocars used in coelioscopic surgery generally have arelatively small calibrated diameter, which may vary, for example, from5 to 15 mm, in order to reduce the size of the incision made as much aspossible. The prosthesis must therefore be conveyed within a channel ofreduced diameter and it must then be deployed at the implantation site.

In order to carry out this step, the prosthesis is generally rolled upon itself in order to make it slide in the channel of the trocar ordirectly introduced by force. However, when the prosthetic fabricforming the prosthesis comprises barbs on one face, it may happen thatthese barbs become entangled in the body of the fabric and upset thesubsequent deployment of the prosthesis at the implantation site.Furthermore, due to the fact that they are not protected, the barbs maybe damaged during the unrolling of the prosthesis or during itstransportation through the trocar to the implantation site.

Thus, there remains the need for a prosthetic fabric comprising barbs,that can be used for manufacturing prostheses, such as for exampleabdominal wall reinforcements, capable of being rolled up on itself inorder to be conveyed within a channel such as that of a trocar, withoutdamaging the barbs, and then capable of being completely deployed, andpreferably in an easy manner, once it has reached the implantation sitein the body of the patient.

The present invention aims to meet such a need.

A first aspect of the invention is a prosthetic knit based on at least afirst yarn of biocompatible polymer material defining first and secondopposite and openwork faces, and on at least a second biocompatible andheat-fusible monofilament yarn, forming barbs that protrude outwardsfrom at least said first face and are obtained by melting loopsgenerated by said second yarn, the chart followed for the knitting ofsaid first and second yarns on a warp knitting machine having threeguide bars B1, B2, B3 being the following, according to the ISO 11676standard:

-   -   Bar B1: 1.0/0.1//    -   Bar B2: 1.0/7.7/6.6/7.7//    -   Bar B3: 2.1/5.5/3.4/0.0//

said second yarn following the chart of bar B3.

The knit according to the invention has both openwork faces, whichfavour cell recolonization, and barbs, suitable for hooking intobiological tissues or any other textile, and an ability to be rolled upon itself, then unrolled effortlessly.

The knit according to the invention can be used as is in order toconstitute a reinforcing prosthesis for repairing a hernia, or it mayconstitute one part of a reinforcing prosthesis for repairing hernias:for example, it may be partially or completely coated over part or allof its faces with a coating made of a biocompatible, for examplenon-stick, material; alternatively or in combination, the knit accordingto the invention may be combined with another textile in order to form acomposite reinforcing prosthesis.

In the present application, the expression “openwork face” is understoodto mean that said face comprises openings or pores: these openings orpores are in particular generated by the chart followed for the knittingof the yarns of the knit according to the invention, and may correspondto the various meshes of said knit.

The barbs of the knit according to the invention may protrude from thefirst face substantially perpendicular to the plane of said face oralternatively along one or more planes that are inclined relative to theplane of said face. These barbs are intended to function as fasteningmeans, either by becoming entangled in one or more arrangements ofyarns, fibres, filaments and/or multifilaments of another prostheticfabric, for example in order to form a composite reinforcing prosthesis,or by anchoring directly in the biological tissues, such as for examplean abdominal wall, once the prosthesis comprising this knit orconstituted of this knit is implanted. Generally, these barbs have theshape of a shaft, having the diameter of the yarn used for theirformation, surmounted by a head having a diameter greater than that ofthe shaft.

In the knit according to the invention, the chart followed for theknitting of the yarns of the knit generates a particular structure ofthe knit, that is to say a specific arrangement between the variousopenings of the faces of the knit, the respective size of these variousopenings and the position and distribution of the barbs being such that,even if some of the barbs present on the first face are caused to betrapped within some of the openings present on the second face when theknit is rolled up on itself under the effect of an external stress, suchas for example the stress exerted by the surgeon when he rolls the knitor the prosthesis comprising the knit up on itself in order to introduceit into a trocar, and subsequently the stress exerted by the internalwalls of the trocar, then a large number of the barbs trapped will bereleased automatically, or under the effect of a very small unrollingforce, when said stress is relieved.

The knit according to the invention can be used to produce a reinforcingprosthesis for repairing a hernia. Thus, when the surgeon wishes toimplant a prosthesis formed of a knit according to the invention, he caneasily roll the knit up on itself, for example by folding the faceprovided with barbs outwards. It is then possible to introduce the knitaccording to the invention, thus rolled up, into a trocar, for examplehaving an internal diameter of 10 mm. Once the knit according to theinvention has been thus conveyed in the form of a roll to theimplantation site via the trocar, it can be unrolled and deployedeasily: indeed, even if some of the barbs were trapped within some ofthe openings present on the second face of the knit during the rollingup of the knit according to the invention and during its passage in thetrocar, the particular structure of the knit according to the inventionobtained by means of the particular chart followed during the knittingof the knit according to the invention means that these trapped barbscan be released very easily by exerting a minimal force for unrollingthe knit. Thus, even if the barbs were entangled when the prosthesis wasrolled up, they can be easily disentangled, and the surgeon can deploythe knit and/or the prosthesis easily in order to position it correctlyon the implantation site.

The knit can then be fastened either to another fabric, or to abiological wall, owing to the anchoring abilities of the barbs.

In one embodiment of the invention, the first yarn or yarns aremonofilament yarns. The first yarn or yarns of the knit according to theinvention are those that follow the charts of bars B1 and B2. Theyconstitute the ground structure or alternatively the base of the knitaccording to the invention, since the second yarn, namely a heat-fusiblemonofilament yarn, so as to generate the barbs, is regularly cut at theloops that it forms. The generation of barbs from loops made ofheat-fusible yarn is known and is described, for example in document WO01/81667. When the first yarn or yarns are monofilament yarns, thepossible presence of protrusions or anchorage points of the barbs islimited and the force needed to unroll the knit after the rolling up asdescribed above is very small.

The first yarns of the knit according to the invention may be made ofany biodegradable or non-biodegradable biocompatible material. Thus, thebiodegradable materials suitable for the first yarns of the knit of thepresent invention may be selected from polylactic acid (PLA),polyglycolic acid (PGA), oxidized cellulose, polycaprolactone (PCL),polydioxanone (PDO), trimethylene carbonate (TMC), polyvinyl alcohol(PVA), polyhydroxyalkanoates (PHAs), copolymers thereof and mixturesthereof. The non-biodegradable materials suitable for the first yarns ofthe knit of the present invention may be selected from polyethyleneterephthalate (PET), polyamides, aramids, expandedpolytetrafluoroethylene, polyurethane, polyvinylidene difluoride (PVDF),butyl ester polymers, polyetheretherketone (PEEK), polyolefins (such aspolyethylene or polypropylene), polyethers, copper alloys, silver orplatinum alloys, medical grades of steel such as medical-grade stainlesssteel, and combinations thereof.

In one embodiment of the invention, the first yarns are monofilamentyarns made of polyester terephthalate (PET) having a diameter of 0.09mm. Such yarns have an intrinsic stiffness meaning that when these yarnsfollow the particular charts of bars B1 and B2 of the knit according tothe present invention, the knit obtained naturally tends to return to aflat configuration when it is unrolled under the effect of a stress asdescribed above.

The second heat-fusible monofilament yarn may be made of a bioresorbableor non-bioresorbable material. For example, the heat-fusiblemonofilament yarn is made of a material selected from polypropylene,polyglycolic acid, polylactic acid, and mixtures thereof. In oneembodiment, the heat-fusible monofilament yarn is a polylactic acidmonofilament yarn having a diameter of 0.15 mm: such a yarn having sucha diameter makes it possible to obtain barbs that have good anchoringabilities in biological tissues or in another openwork textile, whilemaintaining the ability of the knit according to the invention to beunrolled easily.

Another aspect of the invention is a process for manufacturing aprosthetic knit as described above, comprising the following steps:

i) knitting, on a warp knitting machine, of biocompatible yarnsdistributed over three guide bars, according to the following chart,according to the ISO 11676 standard:

-   -   Bar B1: 1.0/0.1//    -   Bar B2: 1.0/7.7/6.6/7.7//    -   Bar B3: 2.1/5.5/3.4/0.0//

the yarn threaded on bar B3 being a heat-fusible monofilament yarn thatgenerates loops that protrude outwards with respect to said first face,

ii) cutting, by melting, of each loop, each loop thus generating twobarbs.

In the process according to the invention the yarns threaded on bar B1and bar B2 are the first yarns made of biocompatible polymer material:these yarns may be identical or different. Thus, as seen above, theseyarns may be monofilament yarns, in particular monofilament yarns madeof polyester terephthalate (PET) having a diameter of 0.09 mm.

In one embodiment of the invention, the yarns are threaded one full, oneempty on bars B1 and B2, and one full, three empty on bar B3.

Another aspect of the invention is a knit capable of being obtainedaccording to the above process.

Another aspect of the invention is a prosthesis for repairing a hernia,comprising a knit as described above or obtained according to theprocess described above.

The knit according to the invention and/or the prosthesis according tothe invention may be used in a method for treating a hernia, inparticular the abdominal wall. The knit and the prosthesis according tothe invention are particularly suitable for coelioscopic or laparoscopicsurgery.

The advantages of the present invention are illustrated by means of theexperimental section which follows and the following supporting figures:

FIGS. 1A to 1C: are diagrams showing the charts followed for theknitting of the yarns of the knits according to the invention,

FIG. 2: is a diagram showing a chart followed for the knitting of theyarns of a knit from the prior art,

FIG. 3: is a diagram illustrating the method for rolling up a knit,

FIGS. 4A and 4B: are diagrams illustrating the test for evaluating theforce for unrolling a rolled-up knit,

FIG. 5: shows the curve representing the force applied, in N, as afunction of the extension, in mm, of a knit during the unrollingthereof.

EXAMPLE 1

Produced on a warp knitting machine having three guide bars B1, B2 andB3, were a knit A, according to the invention, and a comparative knit B,the chart of which differs from that of the knit according to theinvention.

Knit A: according to the invention, having the following chart accordingto the ISO 11676 standard:

-   -   Bar B1: 1.0/0.1//    -   Bar B2: 1.0/7.7/6.6/7.7//    -   Bar B3: 2.1/5.5/3.4/0.0//

These charts are illustrated in FIGS. 1A to 1C according to arepresentation known to a person skilled in the art: the chart of bar B1is illustrated in FIG. 1A; the chart of bar B2 is illustrated in FIG. 1Band the chart of bar B3 is illustrated in FIG. 1C.

Bar B1 and bar B2 are each threaded 1 full, 1 empty, with a monofilamentyarn made of polyester terephthalate (PET) having a diameter of 0.09 mm;bar B3, which gives rise to the barbs, is threaded 1 full, 3 empty, witha heat-fusible monofilament yarn made of polylactic acid having adiameter of 0.15 mm.

Knit B: comparative, having the following chart according to the ISO11676 standard:

-   -   Bar B1: 1.0/0.1//    -   Bar B2: 1.0/5.5/1.0/3.3//    -   Bar B3: 2.1/5.5/3.4/0.0//

The chart of bar B2 is illustrated in FIG. 2.

Bar B1 and bar B2 are each threaded 1 full, 1 empty, with a monofilamentyarn made of polyester terephthalate (PET) having a diameter of 0.08 mm;bar B3, which gives rise to the barbs, is threaded 1 full, 3 empty, witha heat-fusible monofilament yarn made of polylactic acid having adiameter of 0.15 mm.

For each of the two knits A and B, bar B3 is the one that leads to theformation of the barbs. Since the bars B3 are threaded in an identicalmanner for the two knits, and these bars have the same chart, thedensity of the barbs, once the loops have been melted, is the same forboth knits.

Once the loops have been melted and the barbs have been formed asdescribed in WO 01/81667, the unrolling properties were evaluated afterrolling these knits up on themselves, according to the following test:

-   -   for each knit, samples of 5 cm×10 cm were cut,    -   as shown in FIG. 3, each sample 1 of knit is rolled up on itself        around a rod 3 having a diameter of 5 mm, the barbs 2 on the        outside, along the direction of the arrow represented in FIG. 3.        The roll obtained is then grasped with tweezers and inserted        into a trocar having an internal diameter of 10 mm, then pushed        until it comes out of the trocar.

On exiting the trocar, as shown in FIG. 4A, the sample 1 in the form ofa roll is mounted on a machine 4 equipped with a cell loaded to 25 N,comprising a fixed part 5 and a moving part 6. Around 2 cm of the sample1 is unrolled and 1 cm of the sample 1 is fastened to the moving part 6.A constant extension rate of 50 mm/min is then applied to the sample 1tested in order to unroll it, and the corresponding force F needed tomaintain said constant extension rate is measured. The force F needed isrecorded as a function of the length L of the unrolled portion of thesample 1 until sample 1 is completely unrolled, as shown in FIG. 4B.During the unrolling of the sample 1, the force force F needed may varyas a function of the resistance encountered. In particular, points ofresistance, for which the force F for successfully unrolling the sample1 must be increased, at least occasionally, may appear during theunrolling.

These “points of resistance” are measured as follows: using measuredvalues of the force F and length L of the unrolled portion as indicatedabove, the curve representing the force F, in newtons, is plotted as afunction of the length L of the unrolled portion in mm, of the sample 1.Next, a threshold value is determined for the force F, for example 0.5N. Each peak of the curve having a value greater than 0.5 N isconsidered to be a point of resistance. An example of such a curve,showing the peaks counted encircled, is represented in FIG. 5. By virtueof this curve, the maximum force needed, Fmax, is also determined.

The results obtained for knit A according to the invention andcomparative knit B are presented in Table I below:

TABLE I Number of Number of ″points of Average Maximum Sample testsresistance″ force (N) force (N) Knit A 16 52 ± 11 1.13 ± 0.33 3.54 ±0.85 Knit B 20 79 ± 8 4.01 ± 0.80 9.56 ± 1.68

As it emerges from this table, the knit according to the invention (KnitA) has significantly fewer points of resistance than the knit from theprior art (Knit B). The average force needed to unroll the knit of theinvention, after it has been rolled up on itself then passed through atrocar having an internal diameter of 10 mm is substantially lower thanthat needed to unroll the knit from the prior art. Likewise, the maximumforce needed to unroll knit A according to the invention is practicallydivided by 3 compared to the maximum force needed in the case of thecomparative knit B.

Thus, the knit according to the invention can be unrolled easily afterhaving been rolled up on itself then passed through a trocar having adiameter of 10 mm. The knit can thus be brought to an implantation siteduring laparoscopic or coelioscopic surgery for repairing a hernia, bymeans of a trocar, then it can be unrolled without the surgeon having toapply considerable force in order to deploy the knit and/or theprosthesis comprising said knit.

1. A prosthetic knit comprising at least a first yarn of biocompatiblepolymer material defining first and second opposite and openwork faces,and at least a second biocompatible and heat-fusible monofilament yarnwhich forms barbs that protrude outwards from at least said first faceand are obtained by melting loops generated by said second yarn, saidfirst and second yarns being knit on a warp knitting machine havingthree guide bars B1, B2, B3, according to ISO 11676 standard and thefollowing chart: Bar B1: 1.0/0.1// Bar B2: 1.0/7.7/6.6/7.7// Bar B3:2.1/5.5/3.4/0.0// said second yarn following the chart of bar B3.
 2. Theknit according to claim 1, wherein the first yarns are monofilamentyarns.
 3. The knit according to claim 2, wherein the first yarns aremonofilament yarns made of polyester terephthalate (PET) having adiameter of 0.09 mm.
 4. The knit according to claim 3, wherein thesecond heat-fusible monofilament yarn comprises a material selected frompolypropylene, polyglycolic acid, polylactic acid, and mixtures thereof.5. The knit according to claim 3, wherein the second heat-fusiblemonofilament yarn is a polylactic acid monofilament yarn having adiameter of 0.15 mm.
 6. A process for manufacturing a prosthetic knit,comprising the following steps: i) knitting, on a warp knitting machine,of biocompatible yarns distributed over three guide bars, B1, B2 and B3,according to the following chart, according to the ISO 11676 standard:Bar B1: 1.0/0.1// Bar B2: 1.0/7.7/6.6/7.7// Bar B3: 2.1/5.5/3.4/0.0//the yarn threaded on bar B3 being a heat-fusible monofilament yarn thatgenerates loops that protrude outwards with respect to said first face,ii) cutting, by melting, of each loop, each loop thus generating twobarbs.
 7. The process according to claim 6, wherein the yarns threadedon bar B1 and bar B2 are monofilament yarns.
 8. The process according toclaim 6, wherein the yarns threaded on bar B1 and bar B2 aremonofilament yarns made of polyester terephthalate (PET) having adiameter of 0.09 mm.
 9. The process according to claim 6, wherein theyarn threaded on Bar B3 is selected from the heat-fusible monofilamentyarns made of a material selected from polypropylene, polyglycolic acid,polylactic acid, and mixtures thereof.
 10. The process according toclaim 6, wherein the yarn threaded on Bar B3 is a polylactic acidmonofilament yarn having a diameter of 0.15 mm.
 11. (canceled)